The pump speed thing confuses me a bit because the water needs to sit in a radiator long enough to cool off. if you look at a car for example it has a thermostat which only opens when the water in the engine block reaches a certain temperature this gives the water that is inside of the Radiator a chance to cool off.
also is silver based paste better? ( or are they all silver based)

It's the opposite of a car rad, the car is designed to maintain a given temp. thus the thermostat. In our case we want the water as cool as possible. The more times per unit of time the water flows through the rad the cooler it will be, simple physics. There will be an optimum flow as far as efficiency goes but as a general rule more flow will yield cooler temps, and that goes for your blocks as well.